In general, an organic light emitting phenomenon indicates conversion of electric energy into light energy by means of an organic material. An organic electronic device using the organic light emitting phenomenon generally has a structure including an anode, a cathode, and an organic material layer interposed therebetween. Herein, in many cases, the organic material layer may have a multi-layered structure having respective different materials in order to improve efficiency and stability of an organic electronic device. For example, it may include a hole injection layer, a hole transport layer, an emitting layer, an electron transport layer, an electron injection layer, and the like.
Materials used as an organic material layer in an organic electronic device may be classified into a light emitting material and a charge transport material, for example, a hole injection material, a hole transport material, an electron transport material, an electron injection material, etc. according to their functions. Then, the light emitting material may be divided into a high molecular weight type and a low molecular weight type according to their molecular weight, and may be divided into a fluorescent material from electronic singlet excited states and a phosphorescent material from electronic triplet excited states according to their light emitting mechanism. Further, the light emitting material can be classified into a blue, green or red light emitting material and a yellow or orange light emitting material required for giving a more natural color, according to a light emitting color.
Meanwhile, when only one material is used as a light emitting material, an efficiency of a device is lowered owing to a maximum luminescence wavelength being shifted to a longer wavelength due to the interaction between the molecules, the deterioration of color purity and the reduction in luminous efficiency. Therefore, a host/dopant system can be used as the light emitting material for the purpose of enhancing the color purity and the luminous efficiency through energy transfer. It is based on the principle that if a small amount of a dopant having a smaller energy band gap than a host forming an emitting layer is mixed with the emitting layer, excitons which are generated in the emitting layer are transported to the dopant, thus emitting a light having a high efficiency. Here, since the wavelength of the host is shifted according to the wavelength of the dopant, a light having a desired wavelength can be obtained according the kind of the dopant.
In order to allow the organic electronic device to fully exhibit the above-mentioned excellent characteristics, a material constituting the organic material layer in the device, for example, a hole injection material, a hole transport material, a light emitting material, an electron transport material and an electron injection material should be essentially composed of a stable and efficient material. However, the development of a stable and efficient organic material layer material for the organic electronic device has not yet been fully realized. Accordingly, the development of new materials is continuously desired.